Within the past ten years, it has become fairly common to package certain viscous liquids, such as soaps, shampoos and like products, in disposable cartridges and to dispense such liquids from dispensers in places like public washrooms, and hotel and motel bathrooms. Although the detailed construction of the disposable cartridges may differ, they generally include a compressible pump portion and an exit orifice for the liquid. When pressure is applied to the pump portion of the cartridge, liquid is forced through the exit orifice, into the user's hand. The dispensers that accept such disposable liquid cartridges have a manually operated dispensing member, such as a pivoted lever, for pressing the pump portion of the cartridge against a compression surface in the dispenser. A typical prior art viscous liquid dispenser is disclosed in Norman et al. U.S. Pat. No. 4,130,224, assigned to the assignee of the present invention. The dispenser disclosed in that patent is used to dispense liquids such as soap from a single disposable cartridge. The dispenser has a sight window located adjacent to the bottom of the disposable cartridge so that a maintenance person can see that the cartridge needs to be replaced. One problem with the single cartridge dispenser is that when the maintenance person looks at the window, the level of the fluid may be only slightly above the window with the result that the cartridge is completely used up before the maintenance person returns to service the dispenser. Another common occurrence is that if the maintenance person observes that the liquid level in the cartridge is just below the top edge of the sight port, the maintenance person may replace the cartridge rather than take the chance that the cartridge will empty before the dispenser is next serviced. This, of course, can lead to a considerable waste of the liquid soap or other product. Thus, it would be desirable to have a dispenser that holds two disposable cartridges so that the user can completely exhaust one cartridge and then begin immediately dispensing from the second cartridge.
One approach for dispensing from two cartridges is suggested by Hogan U.S. Pat. No. 4,513,885 which discloses packaging two single cartridge dispensers side by side to form a dispensing system. One problem with adopting this concept for a liquid soap dispenser is that since the user can dispense from either dispenser it is possible for both cartridges to empty at the same time. Thus, it can be seen that it would be desirable to have a dual cartridge dispensing system which prevents the user from dispensing from one cartridge until the other cartridge is completely empty.
Dalrymple U.S. Pat. No. 2,619,386 discloses a trigger operated spray gun for simultaneously spraying two liquid solutions onto an object. At column 5, lines 49-68, Dalrymple describes a trigger operated mechanism that simultaneous opens or closes a pair of fluid passages. At column 6, lines 33-40, Dalrymple provides for individual adjustment of the fluid flow through each fluid passageway.
It is an object of this invention to provide a dispenser for two or more disposable, viscous liquid cartridges wherein the probability that the dispenser will empty before it can be serviced is greatly reduced.
Another object of this invention is to provide a dispenser, having two disposable liquid cartridges, that can only dispense from one cartridge at a time.